Treatment of wool with acid anhydrides in the presence of dimethyl sulfoxide



United States Patent 3,079,215 TREATMENT OF W001. WITH ACE) ANHYDRIDES IN TIE PRESENCE OF DIMETHYL SULFOXIDE Nathan H. Koenig, Berkeley, Calif., assignor to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Nov. 21, 1960, Ser. No. 70,892 12 Claims. (Cl. 8-128) (Granted under Title 35, US. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates broadly to the chemical modification of wool by reacting it with an organic acid anhydride. In particular, the invention concerns and has as its prime object the provision of processes wherein the reaction of wool with organic acid anhydrides is conducted in the presence of dimethyl sulfoxide. Further objects and advantages of the invention will be apparent from the following description wherein parts and percentages are by weight, unless otherwise specified.

Prior to this invention it has been advocated that wool be modified by applying an acid anhydride to the wool followed by baking the treated wool in an oven. In another technique, the wool is heated with a solution of acid anhydride in an organic solvent such as benzene or carbon tetrachloride. Under these conditions only a minor amount of acid anhydride actually reacts with the wool so that the degree of modification is low.

In accordance with the present invention, wool is reacted, under essentially anhydrous conditions, with an acid anhydride of the class consisting of aliphatic, aromatic, and aromatic-aliphatic acid anhydrides, in the presence of dimethyl sulfoxide. The latter compound catalyzes the actual chemical combination of the wool and the acid anhydride reactant. As a consequence one is enabled to readily prepare wools containing substantial proportions of combined acid anhydride with correspondingly improved properties. Prior hereto, tertiary amines such as pyridine have been employed as catalysts in reacting acid anhydrides with compounds containing active hydrogen atoms, i.e., primary amines, alcohols, phenols, etc. It has now been established that dimethyl sulfoxide is at least as active as pyridine in catalyzing reaction between wool and acid anhydrides. Moreover, dimethyl sulfoxide is cheaper than pyridine, and has a mild odor in contrast to the offensive odor of pyridine. Also, dimethyl sulfoxide involves a lesser toxicity problem than pyridine and less fire hazard because of a lower order of vapor pressure. Further, the high boiling point of dimethyl sulfoxide (189 C.) makes it possible to conduct the wool-acid anhydride reaction at higher temperatures without requiring pressure-tight vessels or other special apparatus. All of these items indicate that dimethyl sulfoxide is a very useful catalyst for the reaction in question and one which involves many advantages over agents previously described.

The unusual and effective action of dimethyl sulfoxide as a catalyst for the reaction of acid anhydrides with wool is exemplified by the following comparative tests: (a) Dry wool flannel (1.2 g.) and heptenylsuccinic anhydride (6 ml.) were heated for 30 minutes at 105 C. The wool was then extracted with acetone and ethanol to remove unreacted reagents and dried. It was found that the ini033 an 3,079,215 Patented Feb. 26, 1963 "ice crease in weight of the wool was only 2%. (b) Dry wool flannel (1.2 g.) was heated with heptenylsuccinic anhydride (1 ml.) and dimethyl sulfoxide (5 ml.) at 105" C. for 30 minutes. The wool was extracted as described above and dried. In this case, the increase in weight of the wool, due to reaction with the acid anhydride, was 27%.

The fact that dimethyl sulfoxide acts as a catalyst rather than a mere solvent is demonstrated by the following experimental data: Dry wool flannel (1.2 g.), heptenylsuccinic anhydride (2 ml.) and dimethyl sulfoxide (4 ml.) were heated for one-half hour at 105 C. The wool was extracted with acetone and ethanol to remove unreacted reagents and dried. It was found that the increase in weight of the wool, due to reaction with the anhydride, was 28%. A series of experiments were then carried out under the same conditions but substituting for the dimethyl sulfoxide the same volumeof the following solvents: butyl acetate, chlorobenzene, and xylene. In these runs, the increase in weight of the wool was only 2%.

Carrying out the process of the invention essentially involves contacting wool with an acid anhydride in the presence of dimethyl sulfoxide. The reaction conditions such as proportion of reagents, specific acid anhydride used, time, temperature, etc., are not critical but may be varied to suit individual circumstances without changing the basic nature of the invention. The proportion of dimethyl sulfoxide may be varied widely and may be as low as 0.2 volume per volume of acid anhydride. In the case of acid anhydrides which are normally solid, the volume considered is that of the molten (liquified) compound. Usually, it is preferred to use a larger proportion of dimethyl sulfoxide, i.e., about 1 to 5 volumes thereof per volume of acid anhydride, to attain an increased catalytic effect. The temperature of reaction may be about from 25 to 130 C. The reaction rate is increased with increasing temperature and a preferred temperature range to expedite the reaction without possibility of damage to the wool is -120 C. The elfect of temperature on the rate of reaction is illustrated by the following: In a series of runs, heptenylsuccinic anhydride (2 ml.) was reacted with dry wool flannel (1.2 g.) in the presence of dimethyl sulfoxide (4 ml.) under varying conditions of time and temperature. Uptakes of acid anhydride obtained under these conditions were as follows.

Uptake of acid Rfiac loll Conditions: anhydride onwool, percent C., hour 33 Conventional inert solvents such as chlorobenzene, toluene, or butyl ether may be added to the reaction system. The use of a solvent is especially indicated where the acid anhydride used is a solid and the proportion of dimethyl sulfoxide is not sufiicient to dissolve the acid anhydride. It is preferred to carry out the reaction under anhydrous conditions thereby to ensure reaction between the wool and the acid anhydride. The degree of modification of the wool is related to the proportion of acid anhydride taken up by the fiber, that is, the higher the uptake of acid anhydride the greater will be the modification o fthe wool. In general, the uptake of acid anhydride may be varied about from 1 to 35% by weight.

In conducting the reaction, the acid anhydride is generally employed in excess over the amount desired to be taken up by the fiber. The time of reaction will vary depending on the proportion of dimethyl sulfoxide, temperature of reaction, reactivity of the acid anhydride selected, and the degree of modification desired. In general, the reaction may take anywhere firom a few minutes to several hours.

The process in accordance with the invention may be carried out in various ways. For example, the wool may be directly contacted with the dimethyl sulfoxide and acid anhydride reactant and the reaction mixture preferably heated as indicated above to cause the acid anhydride to react with the wool. In the a ternative, the wool may be pretreated with dimethyl sulfoxide and the acid an hydride then added to the mixture and the reaction carried out as previously described. The pretreatment may be carried out at normal temperature or with application or heat, i.e., at -130 C.

After reaction of the wool with the acid anhydride, the chemically modified wool is preferabiy treated to remove excess acid anhydride, reaction by-products, dimethyl sulfoxide, and solvent, if such is used. Thus, the wool may be treated as by wringing, passage through squeezero lls, centrifugation, or the like to remove the excess materials. In-place of such mechanical action, or following it, the product may be extracted with an inert volatile solvent such as trichlorethylene, benzene, acetone, carbon tetrachloride, alcohol, etc. Successive extractions with dilferent solvents may be used to ensure complete removal of all unreacted materials. The treated wool is then dried in the usual way.

By treating wool with acid anhydrides as herein described, the wool is chemically modified because there is a chemical reaction between the acid anhydride and the protein molecules of the wool fibers. As a result the modified wool exhibits many advantageous properties over normal wool. Several of these items are explained below:

An advantageous feature of the invention is the increased resistance of the modified wool to acids as indicated by its decreased solubility in hot hydrochloric acid. This factor improves the usefulness of the modified Wool in applications where the product comes into contact with acidic materials. For example, wool may encounter acid conditions during manufacturing processes such as carbonizing to remove burrs; dyeing in acid dye baths; and tfulling with acid media. The more resistant the wool is to such acid environments, the greater will be its subsequent mechanical strength and wear resistance.

The modified wool is in many cases more resistant to oxidizing conditions. Such conditions may be encountered in textile mills during bleaching, shrinkproofing, or other finishing processes. Oxidizing environments also occur in use by the action of light and air and in laundering by bleaching chemicals. The increased resistance to acid oxidizing conditions is illustrated by the lowered solubility of the modified wool in the peracetic acidamrnonia test described hereinbelow. In addition, resistance to alkaline oxidizing conditions has been shown by exposing normal and modified wool samples to solutions of sodium hypochlorite, which is used in commercial bleaches.

The tendency of wool to shrink when subjected to washing in aqueous media has long been a deterrent to the more widespread use of wool. An advantage of the invention is that it yields modified wools which have a decreased tendency to shrink when subjected to washing with conventional soap and water or detergent and water formulations.

Although the properties of the modified wool indicate beyond question that actual chemical combination between the wool and the acid anhydride has taken place, it is not known for certain how the wool and acid anhydride moieties are joined. -It is believed, however, tha the acid anhydride reacts with some of the sites on the wool molecule where there are reactive hydrogen atoms, e.g., amino, guanidino, hydroxyl, and phenolic groups. It may be, however, that other reactions occur and it is not intended to limit the invention to any theoretical basis. When the reaction is carried out with poly-basic acid anhydrides, .for example, pyrornellitic dianhydride, combination with the wool may establish cross-links between protein molecules of the wool that further increase the resistance of the fibers to chemical attack.

It is to be particularly noted that the reaction in accordance with the invention does not impair the wool fiber for its intended purpose, that is, for producing woven or knitted textiles, garments, etc. The process of the in.- vention may be applied to wool in the form of fibers, as such, or in the form of threads, yarns, slivers, rovings, knitted or woven goods, felts, etc. The wool textiles may be white or dyed goods and may be of all-wool composition or blends of wool with other textile fibers such as cotton, regenerated cellulose, viscose, animal hair, etc.

The invention is of particular advantage in reacting wool with acid anhydrides of higher molecular weightthat is, those with more than eight carbon atoms. Such anhydrides are notorious for their inability to react with wool when using known procedures. However, by applying the process disclosed herein such anhydrides can be caused to react readily with Wool.

Although the invention is particularly adapted for reacting wool with acid anhydrides containing more than eight carbon atoms, the catalytic effect of dimethyl sulfoxide is not restricted to any particular acid anhydride or class of acid anhydrides. Consequently, the invention may be applied in the reaction of wool with all types of organic acid anhydrides. Particularly preferred are the aliphatic, aromatic, and aromatic-aliphatic compounds containing one or more of the characteristic anhydride linkages, that is, the group The anhydrides may be hydrocarbon acid anhydrides or may contain substituents on the hydrocarbon residues such as halogen (chlorine, bromine, iodine, or fluorine), ether groups, ester groups, nitro groups, carboxy groups, etc. Examples of compounds coming within the purview of the invention are listed below by way of illustration and not limitation:

Typical examples of compounds in the category of aliphatic acid anhydrides are acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, isovaleric anhydride, trimethylacetic anhydride, caproic anhydride, caprylic anhydride, capric anhydride, lauric anhydride, myristic anhydride, palmitic anhydride, stearic anhydride, arachidic anhydride, crotonic anhydride, angelic anhydride, oleic anhydride, elaidic anhydride, linoleic anhydride, linolenic anhydride, maleic anhydride, furnaric anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, suberic anhydride, azelaic anhydride, sebacic anhydride, heptylsuccinic anhydride, octylsuccinic anhydride, decylsuccinic anhydride, dodecylsuccinic anhydride, heptenylsuccinic anhydride, octenylsuccinic anhydride, dodecenylsuccinic anhydride, tetrapro' penylsuccinic anhydride, octadecenylsuccinic anhydride, tricosenylsuccinic anhydride, pentatriacontenylsuccinic anhydride, chloroacetic anhydride, bromoacetic anhydride, iodoacetic anhydride, fluoroacetic anhydride, 9,10-dichlorooctadecanoic anhydride, ethoxyacetic anhydride, carbethoxyacetic anhydride, ctfi-diChlOIOSuCCiniC anhydride, cyclohexane-carboxylic anhydride, etc. Of the aliphatic acid anhydrides, it is preferred to use the anhydrides which contain at least eight carbon atoms, particularly aliphatic monobasic acid anhydrides containing at least 8 carbon atoms. These compounds are preferred as they confer on the treated wool especially desirable properties,

- including resistance to acids, oxidizing agents, and shrinkage.

Typical examples in the category of aromatic acid anhydrides are benzoic anhydride, ortho-toluic anhydride, meta-toluic anhydride, para-toluic anhydride, napthoic anhydride, dodecylbenzoic anhydride, orthochlorobenzoic anhydride, meta-chlorobenzoic anhydride, para-chlorobenzoic anhydride, 2,4-dichlorobenzoic anhydride, nitrobenzoic anhydride, phthalic anhydride, isophthalic anhydride, terephthalic anhydride, tetrachlorophthalic anhydride, pyromellitic dianhydride, etc.

Typical examples in the category of aromatic-aliphatic anhydrides are phenylacetic anhydride, chlorophenylacetic anhydride, fi-phenylpropionic anhydride, phenoxyacetic anhydride, etc.

Any of the mixed anhydrides may be employed, for example, aceticlauric anhydride, acetic-stearic anhydride, acetic-oleic anhydride, propionic-palmitic anhydride, acetic-butyric anhydride, acetic-benzoic anhydride, benzoicstearic anhydride, acetic-naphthenic anhydride, di-aceticsuccinic anhydride, di-acetic-dodecenylsuccinic anhydride, etc.

The invention is further demonstrated by the following illustrative examples:

Example I A 4-gram sample of dry wool flannel was heated in an enameled tray with 8 ml. of n-octenylsuccinic anhydride and 17 ml. of dimethyl sulfoxide for 45 minutes at 105 C. The treated fabric was removed from the tray and extracted by rinsing and wringing in warm acetone. t was then extracted with ethanol for 16 hours in a Soxhlet apparatus, dried and weighed. The uptake of anhydride, calculated from the gain in weight of the dried sample, was 26% Example II A 4-gram sample of dry wool flannel was reacted with 8 grams of n-octadecenylsuccinic anhydride and 30 ml. of dimethyl sulfoxide for 60 minutes at 105 C. The treated wool was extracted as in Example I. The uptake of anhydride by the wool was 29%.

Example 111 A 4-gram sample of dry wool flannel was reacted with 5 ml. of ll-tricosenylsuccinic anhydride and 20 ml. of dimethyl sulfoxide for 45 minutes at 105 C. The treated wool was extracted as described in Example I. The uptake of anhydride by the wool was 26%.

Example IV An S-gram sample of dry wool flannel was reacted with 7 ml. of propionic anhydride and 33 ml. of dimethyl sulfoxide for 45 minutes at 105 C. The treated wool was extracted as in Example I. The uptake of anhydride by the wool was 6%.

Example V A 4-grarn sample of dry wool flannel was reacted with 2.4 grams of maleic mihydride and 30 ml. of dimethyl sulfoxide for 30 minutes at 105 C. The treated wool was extracted as in Example I. The uptake of anhydride by the wool was 13% Example VI A 4-gram sample of dry wool flannel was reacted with 2 grams of pyromellitic dianhydride and 25 ml. of dimethyl sulfoxide for 60 minutes at 105 C. The treated wool was extracted as described in Example I. The uptake of anhydride by the wool was 16% Example VII A series of runs were carried out in Petri dishes wherein dry wool flannel was reacted with various acid anhydrides in the presence of dimethyl sulfoxide. In these runs, the weight of dry wool was 1.2 grams and the temperature of reaction was 105 C. The acid anhydrides used, the volume of reagents, the reaction time, and the uptake of acid anhydrides are tabulated below:

Amount Volume Uptake or anhyof di- Reaction of acid Acid anhydride used dride, methyl time, anhyml. or g. snltoxide, min. dride,

ml. percent 4 30 8 3 30 26 3 45 33 5 15 16 5 60 25 2 60 28 n-Octadeeenylsuceinie. 5 30 28 ll-Tricosenylsuccinic 5 30 21 Do 5 45 23 17-Pentatriacontcnyls 5 30 16 Phthalic 2g 10 15 6 Pyromellitie (dianhydride) 10 30 8 D0 1 10 60 23 Example VIII The acid solubility of modified wools produced in accordance with the invention and that of untreated wool were determined in the following way: The wool sample is immersed in 4 N hydrochloric acid for one hour at 65 C. The loss in weight of the sample is then determined after thoroughly washingthe acid-soaked wool. The increased resistance of modified wools to hot hydrochloric acid is illustrated by the following data:

Example IX Experiments were carried out to determine the resistance of the modified wools to oxidizing conditions by measuring their solubility in peracetic acid-ammonia. In this test, about 0.4 g. ofwool is treated at room temperature for 24 hours with 100ml. of 2% peracetic acid and finally for 24 hours with 100 ml. of 0.3% ammonium hydroxide. The loss in weight is determined after thorough washing with water. The results obtained are given below:

Uptake of Peracetie acid acid-ammonia Acid anhydride anhydride solubility,

by wool, percent percent None (untreated wool) 0 mp I 13 41 l7-Pentatriacontenylsuccinic 20 31 Example X Experiments were carried out to determine the resistance of the modified wool samples to the action of aqueous sodium hypochlorite, which is commonly used in bleaches. Samples of treated and untreated wool weighing approximately 25 mg. each were placed individually in a beaker containing 2-0 ml. of a 1.8% aqueous sodium hypochlorite solution. The solution was placed on a magnetic stirring apparatus and stirred thoroughly with a magnetic stirring bar. .The time required to disintegrate the sample was noted. The results are set forth in the following table:

Uptake Time to of acid disintegrate Acid anhydride anhydride sample,

by wool, min.

percent None (untreated W001) Propionic 6 21 Heptenylsuccinic 34 21 ll-Tricosenylsuccinic 24 18 17-Pentatriacontcnylsuccinlc 20 0 Example XI Uptake of acid Area Acid anhydrlde anhydride shrinkage,

by wool, percent percent None (untreated W001) 0 49 Heptenylsuccinic 33 6 Tetrapropenylsucciuie 25 0 ll-Tricosenylsuccinic 23 2 17-Pentatriaeontenylsueeinic 16 5 The various alkenyl succinic anhydrides used in the above examples were commercial products having the type formula wherein R is an alkenyl radical. More specifically, the radical R in the various compounds is as follows.

Heptenylsuccinic anhydride:

R is C H n-Octenylsuccinic anhydride:

R is C H (straight chain) Tetrapropenylsuccinic anhydride:

R is C H n-Octadecenylsuccinic anhydride:

R is C H (straight chain) ll-tricosenylsuccinic anhydride:

17-pentatriacontenylsuccinic anhydride:

R is C1sHas- H m st Having thus defined the invention what is claimed is:

1. A process for chemically modifying wool which comprises reacting wool under essentially anhydrous conditions, in the presence of dimethyl sulfoxide, with an acid anhydride of the class consisting of aliphatic, aromatic, and aromatic-aliphatic acid anhydrides.

2. The process of claim 1 wherein the acid anhydride is an aliphatic mono-basic acid anhydride containing at least 8 carbon atoms.

3. The process of claim 1 wherein the acid anhydride is lauric anhydride.

4. The process of claim 1 wherein the acid anhydride is myristic anhydride.

5. The process of claim 1 wherein the acid anhydride is palmitic anhydride.

6. The process of claim 1 wherein the acid anhydride is stearic anhydride.

7. The process of claim 1 wherein the acid anhydride is an alkenyisuccinic anhydride of the formula wherein R is an alkenyl radical of at least 7 carbon atoms.

8. The process of claim 7 wherein R is heptenyl. 9. The process of claim 7 wherein R is octenyl. 10. The process of claim 7 wherein R is dodecenyl. 11. The process of claim 7 wherein R is tricosenyl. 12. The process of claim 7 wherein R is pentatriacontenyl.

References Cited in the file of this patent UNITED STATES PATENTS 2,880,054 Moore Mar. 31, 1959 2,974,003 Koenig Mar. 7, 1961 2,986,445 Koenig May 30, 1961 2,986,798 Koenig et al. June 6, 1961 2,987,370 Lundgren et a1. June 6, 1961 3,007,763 Adams Nov. 7, 1961 OTHER REFERENCES Houtz: Textile Research, November 1950, pp. 786- 793, 800 and 801. (Copy in POSL.) 

1. A PROCESS FOR CHEMICALLY MODIFYING WOOL WHICH COMRPISES REACTING WOOL UNDER ESSENTIALLY ANHYDROUS CONDITIONS, IN THE PRESENCE OF DIMETHYL SULFOXIDE, WITH AN ACID ANHYDRIDE OF THE CLASS CONSISTING OF ALIPHATIC, AROMATIC, AND AROMATIC-ALIPHATIC ACID ANHYDRIDES. 